This disclosure relates to a nozzle unit where a fluid including a coating material is sprayed and a coating apparatus including the same.
Cold spray coating is one of a spray coating method which applies coating by spraying a powder which needs to be coated. Cold spray coating is a process of applying coatings to a material by spraying with high velocity using collision energy with basic material in a room temperature where the material reacts or its coordination does not change, or in a low temperature.
FIG. 1 is a lateral cross-sectional view briefly illustrating inside of a nozzle 1 of a conventional coating apparatus. Referring to FIG. 1, a cold spray coating apparatus supplies a powder and a gas to the nozzle 1. The gas provides a pressure to spray powders. A flow velocity of the gas including powders is the highest in a center 2 of the nozzle 1 by its viscosity. The velocity of the gas decreases as moving to inner lateral wall 3 of the nozzle 1, and gets close to 0 when the gas reaches an area adjacent to the inner lateral wall 3 of the nozzle 1. Due to decrease in velocity, it requires a gas with higher pressure thereby lowering energy efficiency. Also, powder particles moving along the inner lateral wall 3 adjacently have lower momentum. Upon impact with a basic material, the particles experience elastic collision which occur no coatings or some coatings thereby causing a Void and losing the coating material. Therefore, cold spray coating requires long time to form a coating layer due to loss of the coating material and is not simple to form coating layer over certain thickness.